VSAM Interview Questions with Detailed Answers and Examples (Continued)

31. How do you determine the optimal CI and CA sizes for a VSAM dataset?

 Control Interval (CI):

o Choose a CI size that minimizes I/O operations while accommodating the average
record size.
o Common sizes: 4 KB, 8 KB, 16 KB.
 Control Area (CA):
o Set a CA size based on the expected dataset size and growth.

Example of CI and CA configuration:

DEFINE CLUSTER (
NAME(MY.KSDS.FILE)
RECORDSIZE(80 100)
CISZ(4096)
)

32. What are the differences between the REPRO, EXPORT, and IMPORT
commands in VSAM?

 REPRO: Copies data between datasets or files.

 EXPORT: Creates a backup of a VSAM dataset to a flat file.
 IMPORT: Restores a VSAM dataset from a flat file.

Example for REPRO:

//STEP1 EXEC PGM=IDCAMS

//SYSPRINT DD SYSOUT=A
//SYSIN DD *
REPRO INFILE(INPUT) OUTFILE(OUTPUT)
/*

33. What is the SHAREOPTIONS parameter in VSAM?

The SHAREOPTIONS parameter controls concurrent access to a VSAM dataset.

 SHAREOPTIONS(1,3): Allows one user for read/write and multiple users for read-only.
 SHAREOPTIONS(2,3): Allows multiple users for read/write and read-only.

Example:

DEFINE CLUSTER (
NAME(MY.KSDS.FILE)
SHAREOPTIONS(1,3)
)

34. How can you compress a VSAM dataset?

VSAM does not natively support compression. However, you can use third-party utilities like
DFSMS or compress data at the application level before storing it.

35. How do you delete specific records from a VSAM dataset?

You can use a COBOL program or the IDCAMS DELETE command for specific records.

Example:

//STEP1 EXEC PGM=IDCAMS

//SYSPRINT DD SYSOUT=A
//SYSIN DD *
DELETE MY.KSDS.FILE RECORD(RECORD-ID)
/*

36. How do you convert a sequential file to a VSAM file?

1. Define the VSAM file.

2. Use the REPRO command to copy the sequential file to the VSAM file.

Example:

//STEP1 EXEC PGM=IDCAMS

//SYSPRINT DD SYSOUT=A
//SYSIN DD *
DEFINE CLUSTER (
NAME(MY.KSDS.FILE)
RECORDSIZE(80 100)
INDEXED
)
REPRO INFILE(INPUT) OUTFILE(MY.KSDS.FILE)
/*

37. How do you handle out-of-space conditions in VSAM?

1. Use the EXTEND option while defining the dataset.

2. Allocate sufficient secondary space during dataset definition.

Example:
DEFINE CLUSTER (
NAME(MY.KSDS.FILE)
SPACE(1000,500)
)

38. What is the role of the VERIFY command in VSAM?

The VERIFY command ensures the consistency between the catalog and the dataset's physical
structure on disk.

Example:

//STEP1 EXEC PGM=IDCAMS

//SYSPRINT DD SYSOUT=A
//SYSIN DD *
VERIFY DATASET(MY.KSDS.FILE)
/*

39. How do you backup and restore VSAM datasets?

 Backup: Use the EXPORT command.

 Restore: Use the IMPORT command.

Backup example:

EXPORT MY.KSDS.FILE OUTFILE(EXPORT.DUMP)

Restore example:

IMPORT INFILE(EXPORT.DUMP) OUTDATASET(MY.RESTORED.FILE)

40. What is the significance of the NONUNIQUEKEY option in alternate

indexes?

The NONUNIQUEKEY option allows duplicate values for the alternate index key, enabling
multiple records to share the same key.

Example:

DEFINE ALTERNATEINDEX (
NAME(MY.KSDS.FILE.ALTIDX)
RELATE(MY.KSDS.FILE)
KEYS(10 0)
NONUNIQUEKEY
)
41. Explain the concept of dataset compression in VSAM.

VSAM does not provide built-in compression. However, external tools like DFSMS can
compress data for storage efficiency.

42. What is the role of the ERASE option in dataset definition?

The ERASE option ensures that all data in the dataset is erased when it is deleted.

Example:

DEFINE CLUSTER (
NAME(MY.KSDS.FILE)
ERASE
)

43. How do you load data from a flat file to a KSDS file?

1. Define the KSDS file.

2. Use the REPRO command to load the data.

Example:

REPRO INFILE(INPUT) OUTFILE(KSDSFILE)

44. What are some common issues while working with VSAM datasets?

 CI and CA splits.
 Out-of-space errors.
 Incorrect SHAREOPTIONS settings.

45. How do you define reusable datasets in VSAM?

Use the REUSE option:

DEFINE CLUSTER (
NAME(MY.KSDS.FILE)
REUSE
)
46. What is the difference between PRIMARY and SECONDARY allocation?

 PRIMARY allocation: Initial space allocated when the dataset is created.

 SECONDARY allocation: Additional space allocated if the dataset exceeds its primary
allocation.

47. How do you check the free space in a VSAM dataset?

Use the LISTCAT command:

LISTCAT ENTRIES(MY.KSDS.FILE) ALL

48. What is an empty dataset in VSAM?

An empty dataset is a VSAM file with no data records but retains its catalog entry and structure.

49. How do you rename a VSAM dataset?

Use the ALTER command:

ALTER MY.KSDS.FILE NEWNAME(MY.NEW.KSDS.FILE)

50. What is the purpose of the SPANNED keyword?

The SPANNED keyword allows a single record to span multiple control intervals (CIs).

Example:

DEFINE CLUSTER (
NAME(MY.KSDS.FILE)
SPANNED
)

51. What is the function of the STRIPED attribute in VSAM?

The STRIPED attribute enables a dataset to be stored across multiple volumes, improving
performance for large datasets.

Example:
DEFINE CLUSTER (
NAME(MY.KSDS.FILE)
STRIPED
)

52. How do you control record locking in VSAM?

VSAM provides record-level locking to ensure data integrity during updates. COBOL programs
using the START or READ commands can specify the locking behavior.

Example in COBOL:

READ MY-FILE RECORD LOCK

INVALID KEY DISPLAY 'LOCK FAILED'.

53. How can you split a VSAM dataset into multiple datasets?

1. Define the target datasets.

2. Use the REPRO command with conditions or ranges to copy specific records.

Example:

REPRO INFILE(INPUT) OUTFILE(OUTPUT1) IF(KEY LE 'VALUE1')

REPRO INFILE(INPUT) OUTFILE(OUTPUT2) IF(KEY GT 'VALUE1')

54. What is the purpose of the FREECLOSE parameter in VSAM?

The FREECLOSE parameter ensures that a dataset is automatically deallocated when it is closed
by the application, improving resource utilization.

Example:

DEFINE CLUSTER (
NAME(MY.KSDS.FILE)
FREECLOSE
)

55. What is a VSAM RLS (Record-Level Sharing)?

VSAM RLS allows multiple systems to access the same dataset simultaneously with record-level
locking, ensuring data consistency.
1. Introduction to CICS (Customer Information Control System)

CICS is an online transaction processing (OLTP) system that enables high-volume transaction
processing. It is designed to handle multiple users simultaneously, ensuring data consistency and
reliability. CICS is often used in industries like banking, retail, and telecommunications.

 CICS Key Features:

o Multi-tasking: Supports many transactions at the same time.
o Transaction Management: Manages the lifecycle of each transaction.
o Database Access: Provides access to VSAM and DB2 databases.
o Terminal Communication: Supports interaction with terminals.

2. Difference Between Batch & Online Processing

Batch Processing and Online Processing are two different approaches to handling data and
transactions.

 Batch Processing:
o Data is collected over a period of time, then processed together in a single batch.
o Often used for non-time-sensitive tasks like end-of-day processing.
o Example: Generating monthly reports or processing payroll.
 Online Processing (OLTP - CICS):
o Data is processed immediately when a transaction is entered.
o CICS is a classic example of an OLTP system where users can interact with the
system in real time.
o Example: Bank transactions, ticket booking systems, etc.

Real-Time Use Case:

 In a banking system, when a user initiates a transfer, it is processed instantly in an online

system like CICS, while monthly statements might be processed using batch processing.

3. MAP

In CICS, a MAP refers to a user interface that defines the screen layout. A MAP consists of
fields that will be filled by data or user input.

 MAP is used to define the structure of the screen, including all fields, attributes (like
color, type), and control elements.

Real-Time Use Case:

  For a bank transaction application, a MAP might include fields such as Account Number,
Amount, and Transaction Type.

4. MAPSET

A MAPSET is a collection of MAPs. It groups related MAPs together that are used for a
specific application or task. The MAPSET is referenced in the program to define which MAP to
use for the screen.

 MAPSET enables flexibility and structure in screen design and helps in defining multiple
screens under a single group.

Real-Time Use Case:

 A bank application might have a MAPSET for customer transactions with multiple MAPs
for balance inquiry, fund transfer, and account details.

5. SYMBOLIC MAP

A Symbolic MAP is a program-level representation of the physical MAP. It allows for easier
manipulation of data when interacting with the screen. The symbolic MAP holds the data that is
transferred between CICS and the program.

 Symbolic MAPs are typically used to define user-defined variables for screen fields that
are mapped to actual CICS data.

Code Example:

cobol
CopyEdit
01 MAP-DATA.
05 ACCOUNT-NUMBER PIC X(10).
05 AMOUNT PIC 9(6)V99.

This defines symbolic MAP fields for an account number and amount that the program will
interact with.

6. PHYSICAL MAP
The Physical MAP represents the actual screen layout in CICS, defining where each field
appears on the screen. It is used for the actual input/output processing. The program sends or
receives data through this map.

Real-Time Use Case:

 In an ATM system, the physical MAP would define the placement of the fields on the
ATM screen, such as PIN entry, withdrawal amount, and balance display.

7. TRANSACTION, TASK, MULTITASKING, MULTITHREADING

 Transaction: A set of operations that are treated as a single unit of work. In CICS, each
transaction is assigned a unique transaction ID (TID) and is processed independently.
 Task: A task refers to an individual program execution that is initiated by a transaction
request. A task is the smallest unit of work in CICS.
 Multitasking: CICS allows multiple tasks (transactions) to be processed simultaneously.
This allows high throughput in environments where many transactions occur at once.
 Multithreading: Refers to executing multiple threads within a single task, where each
thread can execute a part of the task. CICS traditionally operates with multitasking, but it
can handle multi-threaded operations in modern configurations.

Real-Time Use Case:

 In an online shopping application, multiple users can simultaneously place orders

(multitasking), and a user’s order processing might use multithreading to check
inventory, process payments, and generate shipping labels simultaneously.

8. PSEUDO CONVERSATION

A Pseudo-conversation is a way to simulate interactive sessions in CICS by breaking a long-

running conversation into multiple shorter tasks. This allows CICS to control the flow of
processing by using multiple transactions.

 Each part of the conversation is handled by a different transaction, and CICS ensures the
continuity by storing necessary information between tasks.

Code Example:

cobol
CopyEdit
EXEC CICS START TRANSID('TRAN1')
END-EXEC;
9. CURSOR Positioning Technique

In CICS, cursor positioning refers to controlling the position of the cursor on the screen for
interactive sessions. This allows the program to control where the user will input data.

 Cursor positioning can be done programmatically using specific commands in CICS.

Real-Time Use Case:

 In an online banking application, cursor positioning can place the cursor at the Account
Number field when the user accesses the login screen.

10. Control Programs, Tables

 Control Programs: Programs that manage system-level tasks within CICS. They handle
tasks like transaction routing, transaction management, and resource management.
 Tables: In CICS, tables are used to define various system resources, such as transaction
programs, queues, and file access methods. Tables like the Program Control Table
(PCT) and File Control Table (FCT) are key to defining how CICS operates.

11. Application Programming

Application Programming in CICS involves creating programs (written in COBOL, C, or

PL/I) that interact with CICS resources, like transactions, files, databases, and user interfaces.
CICS provides APIs for programmatically managing these resources.

 Common CICS commands used in application programming include EXEC CICS READ,
EXEC CICS WRITE, and EXEC CICS INQUIRE.

12. Exception Handling in CICS

Exception Handling in CICS involves managing runtime errors and ensuring that a program
responds correctly when errors or unexpected conditions occur.

 CICS Error Codes are generated when a program encounters an error.

 You can use the HANDLE CONDITION command to handle specific exceptions and manage
error recovery.

Code Example:
cobol
CopyEdit
EXEC CICS HANDLE CONDITION(ABEND)
PROGRAM(ERROR_HANDLER)
END-EXEC;

13. Logging into CICS

To log in to CICS, users typically enter a transaction identifier (TID) on a terminal. After the
login, a transaction is executed based on the user's input.

Real-Time Use Case:

 A user logs into an online portal with credentials, triggering a CICS transaction that
validates the credentials and grants access.

14. LINK

LINK is a CICS command that allows one program to call another program within the same
CICS region. It is typically used for calling sub-programs from a main program.

Code Example:

cobol
CopyEdit
EXEC CICS LINK PROGRAM('MYPROGRAM')
COMMAREA(DATAAREA)
END-EXEC;

This command calls the MYPROGRAM and passes data via COMMAREA.

15. XCL (EXCLUDE)

XCL (Exclude) is used in CICS to control the access of resources like files and programs. It is
often used to restrict access to certain files, thereby maintaining data security and integrity.

Real-Time Use Case:

 In a banking system, the system might exclude a file from access during end-of-day
processing to ensure data consistency.
16. TSQ (Temporary Storage Queue)

TSQ is used to store temporary data that can be passed between CICS transactions. It is typically
used to share data within a transaction or pass data between different tasks in a pseudo-
conversation.

Code Example:

cobol
CopyEdit
EXEC CICS WRITEQ TSQUEUE
DATA(DATAAREA)
LENGTH(4)
END-EXEC;

17. TDQ (Transient Data Queue)

TDQ is used to store messages that can be processed by another task or program. Unlike TSQs,
TDQs are typically used for message passing between different systems or tasks.

Real-Time Use Case:

 In a distributed system, a TDQ might be used to send a message from one system to
another for processing.

1. Introduction to CICS

Q1: What is CICS, and what are its primary functions?

Answer: CICS (Customer Information Control System) is an IBM-developed online transaction

processing (OLTP) system that supports rapid transaction handling for applications requiring
high availability and high throughput. CICS is designed to manage multiple tasks concurrently,
providing real-time processing and communication between users and applications.

 Primary Functions:
o Transaction management: Handles multiple user transactions.
o Program management: Manages execution of user programs.
o Data management: Provides access to databases and files.
o Terminal management: Manages communication with user terminals.
Q2: What are some key features of CICS that make it suitable for high-volume transaction
processing?

Answer:

 High Availability: CICS is designed to run continuously with minimal downtime.

 Multitasking: CICS supports multiple transactions running in parallel.
 Recovery and Logging: CICS supports mechanisms like syncpoints to ensure data
integrity in case of system failure.
 Resource Management: It efficiently manages resources like CPU, memory, and I/O
devices to handle high transaction loads.

2. Difference Between Batch & Online Processing

Q1: How does batch processing differ from online processing (OLTP) in CICS?

Answer:

 Batch Processing:
o Processes a large set of data in bulk after gathering it over time.
o Typically used for non-time-sensitive operations (e.g., end-of-month reports).
o Data is processed and stored in one go.
 Online Processing (OLTP):
o Processes transactions in real-time as they occur.
o CICS handles these transactions immediately, providing feedback to the user in
real-time.
o Example: Bank transactions like deposits and withdrawals.

Q2: Can CICS handle both batch and online processing? How?

Answer: Yes, CICS can handle both batch and online processing, although it is predominantly
known for online processing. For batch processing, CICS can manage jobs using batch job
control (through MVS or z/OS), while online transactions are managed through specific CICS
transaction IDs.

3. MAP, MAPSET, Symbolic MAP, and Physical MAP

Q1: What is a MAP in CICS, and why is it important?

Answer: A MAP is a description of the layout of a screen in a CICS application. It defines the
positions of fields, colors, and other screen elements, allowing the program to display data and
interact with the user.

 Importance: It allows for a structured approach to creating user interfaces, ensuring that
input data can be collected from users and displayed on the screen correctly.

Q2: What is a MAPSET, and how does it differ from a MAP?

Answer: A MAPSET is a collection of multiple MAPs. Each MAP defines a specific screen
layout, while a MAPSET groups these layouts together to manage a sequence of related screens.
MAPSETs are useful when creating complex applications with several screens.

Q3: How do symbolic and physical maps differ in CICS?

Answer:

 Symbolic MAP: Represents data structures in the program (like variables for user input
fields). It is easier to manipulate for programming.
 Physical MAP: Defines the actual physical layout of the screen, including the locations
of fields and other interface elements.

4. TRANSACTION, TASK, MULTITASKING, MULTITHREADING

Q1: What is the difference between a transaction and a task in CICS?

Answer:

 Transaction: A user or system request that involves a specific operation, such as account
balance inquiry or fund transfer. It is identified by a unique transaction ID.
 Task: A program unit that is invoked to perform the operations for a transaction. It is the
smallest unit of work in CICS.

Q2: How does multitasking work in CICS?

Answer: CICS uses multitasking to process multiple transactions concurrently. It achieves this
by managing multiple tasks and allocating system resources to handle many users
simultaneously. Tasks run independently, and CICS provides mechanisms to control concurrency
and data integrity.

Q3: What is multithreading, and does CICS support it?

Answer: Multithreading involves executing multiple threads within a single task. While CICS
traditionally uses multitasking to manage concurrent transactions, it supports multithreading in
modern environments (like Java or CICS Transaction Server) for managing multiple operations
within a single task.

5. Pseudo-Conversation

Q1: What is a pseudo-conversation in CICS?

Answer: A pseudo-conversation allows CICS to split a single transaction into multiple tasks
that run over time. Each task performs part of the transaction, and CICS saves intermediate data
(like the state of the transaction) between tasks.

Q2: When would you use a pseudo-conversation in a CICS application?

Answer: You would use a pseudo-conversation in situations where a transaction is too long to
complete in a single execution cycle. For example, when a user enters a large form or provides a
set of responses that need to be processed across several screens.

6. Cursor Positioning Technique

Q1: How does cursor positioning work in CICS?

Answer: Cursor positioning in CICS refers to determining the position of the cursor on the
terminal screen, usually for user input. The program can use cursor positioning to guide users in
filling out forms by placing the cursor at the correct field.

Code Example:

cobol
CopyEdit
EXEC CICS SEND MAP('LOGINMAP') CURSOR(ACCOUNT) END-EXEC;
Q2: Why is cursor positioning important in interactive applications?

Answer: Cursor positioning enhances user experience by guiding the user to the next field or
part of the screen where input is required. It reduces the chance of errors and speeds up the data
entry process.

7. Control Programs and Tables

Q1: What is the role of control programs in CICS?

Answer: Control programs manage system-level operations within CICS, such as transaction
routing, program invocation, and resource management. They ensure that transactions are
processed efficiently and that system resources are allocated appropriately.

Q2: Can you explain what a PCT (Program Control Table) is in CICS?

Answer: The Program Control Table (PCT) defines which programs are associated with
specific transactions in CICS. It helps CICS determine the correct program to execute when a
transaction is initiated.

8. Application Programming

Q1: How do you perform file I/O operations in CICS using COBOL?

Answer: In CICS, file I/O operations are performed using CICS commands such as EXEC CICS
READ, EXEC CICS WRITE, and EXEC CICS REWRITE.

Code Example (Reading from a VSAM file):

cobol
CopyEdit
EXEC CICS READ FILE('VSAMFILE') INTO(DATAAREA) LENGTH(4) END-EXEC;

Q2: What is COMMAREA, and how is it used in CICS?

Answer: The COMMAREA (Communication Area) is a memory area used to pass data
between programs in CICS. It is typically used with the LINK and START commands to exchange
information between programs.

Code Example:
cobol
CopyEdit
EXEC CICS LINK PROGRAM('TRANSFER') COMMAREA(TRANSFER-DATA) END-EXEC;

9. Exception Handling in CICS

Q1: How do you handle exceptions in CICS applications?

Answer: CICS provides a HANDLE CONDITION command to manage exceptions. You can
define specific conditions, such as ABEND (abnormal end), and associate them with custom
error-handling programs.

Code Example (Handling ABEND):

cobol
CopyEdit
EXEC CICS HANDLE CONDITION(ABEND)
PROGRAM(ERROR_HANDLER)
END-EXEC;

Q2: What is the role of the RETURN command in exception handling?

Answer: The RETURN command is used to return control from an exception handler back to
the caller after handling an error. It is commonly used after resolving an exception or performing
necessary error recovery actions.

10. Logging into CICS

Q1: How do users typically log into CICS?

Answer: Users log into CICS by entering a transaction ID on their terminal. After entering the
transaction ID, CICS authenticates the user and begins processing the corresponding transaction.

Q2: How is transaction processing handled after a user logs into CICS?

Answer: After a user logs into CICS, a transaction ID is invoked, and CICS routes the
transaction to the appropriate program based on the Program Control Table (PCT). The
program executes and handles the transaction, interacting with data files and returning results.
11. LINK Command

Q1: What is the LINK command used for in CICS?

Answer: The LINK command is used to call another program from within a CICS transaction. It
allows one program to invoke another to perform specific tasks, and it passes data between the
programs using COMMAREA.

Q2: Can you explain the difference between LINK and START commands in CICS?

Answer:

 LINK: Used to call a program within the same transaction. The transaction remains in
control.
 START: Used to initiate a new transaction and call a program associated with that
transaction. It allows the calling program to pass control to another transaction.

12. XCL (Exclude Command)

Q1: What is the purpose of the XCL command in CICS?

Answer: The XCL (Exclude) command restricts access to certain resources like files and
programs in CICS. It is commonly used to control access to sensitive data or to exclude a
resource during specific periods (e.g., end-of-day processing).

Q2: How does CICS handle resource access control?

Answer: CICS controls resource access through the XCL command and by defining access
permissions in resource tables like File Control Table (FCT) and Program Control Table
(PCT). This ensures that only authorized programs or transactions can access specific resources.

13. TSQ (Temporary Storage Queue)

Q1: What is a TSQ, and when would you use it?

Answer: A TSQ (Temporary Storage Queue) is used to store temporary data in memory that can
be passed between transactions. It is often used in pseudo-conversations to store intermediate
results or data that needs to be processed later.
Code Example (Writing to TSQ):

cobol
CopyEdit
EXEC CICS WRITEQ TSQUEUE DATA(DATAAREA) LENGTH(4) END-EXEC;

Q2: Can you explain the difference between TSQ and TDQ in CICS?

Answer:

 TSQ (Temporary Storage Queue): Stores temporary data in memory. Primarily used
for intra-transaction data passing.
 TDQ (Transient Data Queue): Stores messages for inter-transaction or inter-system
communication.

14. TDQ (Transient Data Queue)

Q1: What is a TDQ in CICS, and what is it used for?

Answer: A TDQ (Transient Data Queue) is used for storing messages that can be retrieved by
other tasks or programs. It allows for communication between different tasks or even different
systems.

Q2: How does a TDQ differ from a TSQ?

Answer:

 TDQ: Used for message passing across systems or tasks. It provides inter-transaction
communication.